1. Field of the Invention
This invention relates to a shock absorbing, rotary drive coupling unit for drivingly connecting a tubular drive shaft to an axially aligned tubular driven shaft of a rotary blast hole drill.
2. Description of the Prior Art
Heretofore, couplings have been used to drivingly connect the drive means of a blast hole drill to the upper end of a string of drill steels. One such coupling is generally indicated in U.S. Pat. No. 3,951,470, issued Apr. 20, 1976, to Donald F. McLean. A specific form of coupling device for this purpose is disclosed in U.S. Pat. No. 3,947,009, issued Mar. 30, 1976, to Jack D. Nelmark.